As a serial-killer movie, Patty Jenkinsís Monster is obliged to detail the killerís crimes; to try to explain them (even if only to reject its own explanations, as Gus Van Sant does in Elephant); to harrow the audience with random death; and then to offer, or deny, solace. Jenkinsís real-life subject ó Aileen Wuornos (Charlize Theron), an abused child who became a prostitute who killed her johns ó provides plenty of material for a feminist analysis. And the way the narrative focus on Wuornosís relationship with her girlfriend (Christina Ricci) allows Jenkins to explore the problems of gay women in middle America.

But in trying to reconcile these ambitions and obligations, Jenkins falters. In the murder scenes, Monster falls into a trap that was always going to be difficult to avoid: the victims must be seen either to deserve their fates (because they are themselves victimizers) or not, whereas the killer must be perceived either as an avenging angel or as a horribly misguided idealist. Monster is thus forced to say too much about the killings, to tie them too neatly to the heroineís thematic plight. But Theronís performance is a discomforting tour de force, and Bruce Dern is excellent in a small role. (110 minutes) At the Boston Common and the Kendall Square and in the suburbs.